1. Field of the Invention
The invention relates to a control apparatus for an internal combustion engine.
2. Description of Related Art
Some internal combustion engines are configured such that vaporized fuel generated in a fuel tank flows, together with air, into an intake passage as purge gas through a vaporized fuel processing device. In such an internal combustion engine, if the concentration of fuel in the purge gas is not taken into account in executing fuel injection amount control, the amount of fuel injected into the engine (hereinafter, simply referred to as “fuel injection amount”) deviates from its proper value and such a deviation exerts an adverse effect on the air-fuel ratio in the engine. In view of this, the concentration of fuel in the purge gas flowing into the intake passage is learned as a vapor concentration learned value, and the vapor concentration learned value is reflected in an injection amount command value used for the fuel injection amount control for the internal combustion engine. In this way, the fuel injection amount is inhibited from deviating from its proper value due to an inflow of the purge gas into the intake passage.
In addition, a throttle valve that adjusts the intake air amount is provided in the intake passage of the internal combustion engine, and the purge gas is caused to flow into the intake passage with the use of a negative pressure generated in a portion of the intake passage downstream of the throttle valve. However, in an internal combustion engine with a turbocharger, such a negative pressure is less likely to be generated, and thus the purge gas is also caused, by a pump, to flow into a portion of an intake passage upstream of a throttle valve.
In this case, as described in Japanese Patent Application Publication No. 2007-332855 (JP 2007-332855 A), a portion of an intake passage downstream of a throttle valve is provided with a first inlet through which purge gas is caused to flow into the intake passage with the use of a negative pressure, whereas a portion of the intake passage upstream of the throttle valve is provided with a second inlet through which the purge gas is caused to flow into the intake passage with the use of a pump. The inlet through which the purge gas flows into the intake passage is switched between the first inlet and the second inlet, depending on, for example, the state of a negative pressure generated in the portion of the intake passage downstream of the throttle valve.